As switching power source devices of this type, configurations have been proposed that are capable of accepting AC commercial power sources having different voltages and each of which includes a full-wave rectifier circuit rectifying AC voltage from the AC commercial power sources and a transformer inputting rectified AC voltage to the primary side thereof and outputting DC voltage from the secondary side thereof (see, for example, JP 2011-244660 A). In a conventional technology described in JP 2011-244660 A, it is configured such that voltage on the primary side of a transformer is detected, the gain of an amplifier used for current sensing is altered according to the detected voltage, and a switching element connected to the primary side of the transformer is on/off controlled by means of amplified output from the amplifier.
A switching power source device is generally configured in such a manner that a boost chopper including an inductor and a switching element are interposed between a full-wave rectifier circuit and the primary side of a transformer and the switching element in the boost chopper is on/off controlled by a power factor correction circuit (see, for example, JP 2011-103725 A). In a conventional technology described in JP 2011-103725 A, a power factor correction circuit includes a voltage error amplifier circuit, a multiplier, a current error amplifier circuit, and a PWM comparator. The voltage error amplifier circuit accepts input of feedback voltage representing output voltage from a boost chopper and reference voltage and amplifies and outputs difference voltage between the feedback voltage and the reference voltage. The multiplier multiplies the output from the voltage error amplifier circuit by output voltage from a full-wave rectifier circuit. The current error amplifier circuit accepts input of the output from the multiplier and voltage obtained by inverting-amplifying voltage obtained by sensing inductor current as negative voltage and amplifies and outputs difference voltage between both inputs. The PWM comparator, by comparing a carrier signal from an oscillator circuit with the output from the current error amplifier circuit, generates a pulse-width modulated control signal and supplies a switching element in the boost chopper with the control signal.